Hold down the Cmnd/Ctrl key while scrubbing (this is an AE basic you'll find info on in the help files)
I do a lot of dynamic text animations. Scrubbing the timeline and poking around the timeline trying to set timing is very inefficient. A better technique is to open your audio track (should be an aiff or wav file) in Premiere Pro, open the meta data panel, analyze the sound, then save the file. When you then bring the audio track into AE you'll see the words as markers. This saves a bunch of time. You can also load in a text file of the script to assure that you have 100% perfect speech to text.
You end up with this:
You can use the j and k keys to snap back and forth between words. If you set up some animation presets that use the layers in and out point you don't even have to set keyframes. Here's a free one you can have that I use all the time. Slide in-bounce, drop out. Just set the layers in and out point, position the layer where you want it to rest, and apply the preset. Once I've created the artwork and recorded the audio track I can have a 3 minute dynamic text animation ready to render in about two hours. Doing it by hand using your technique would take two or three days. Build up your preset library, learn expressions, and be efficient.
You can learn how to analyze speech right here on Adobe TV
It's amazing what you will find if you type a question in the Search After Effects Help field right inside AE.
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